Wireless telephones, such as mobile/cellular telephones, cordless telephones, and other consumer audio devices, such as mp3 players, are in widespread use. Performance of such devices with respect to intelligibility can be improved by providing noise canceling using a microphone to measure ambient acoustic events and then using signal processing to insert an anti-noise signal into the output of the device to cancel the ambient acoustic events. Because the acoustic environment around personal audio devices, such as wireless telephones, can change dramatically, depending on the sources of noise that are present and the position of the device itself, it is desirable to adapt the noise canceling to take into account such environmental changes.
However, an audio device that provides active noise cancellation (ANC) to a listener may provide more ANC effect than the listener desires. Thus, a listener may wish to selectively reduce the amount of ANC. In a noise cancellation system with a fixed feedback filter or a fixed feedforward filter for generating anti-noise, reducing the ANC effect may be easily accomplished by reducing the gain of the anti-noise in the fixed feedback filter, the fixed feedforward filter, or both. On the other hand, in an adaptive system, simply reducing gain of an anti-noise path (whether in the fixed feedback filter, the feedforward filter, or both) may not serve to reduce the ANC effect, as the adaptive system may adapt further to compensate (e.g., undo) the reduction of anti-noise gain. As a result, the ANC effect would return to what it was before the listener reduced the gain. Accordingly, using traditional approaches, a listener has no effective means to reduce ANC effect in an adaptive system.